I'm not sure what you mean. Security updates tend to be a little vague as Apple do not want to tell the bad guys what vulnerabilities they have patched. Updates which tend to add functionality get publicised

I'm not aware that memory itself uses a lot of power. However, processor intensive tasks do use more power and apps with larger memory footprints tend to have larger cpu requirements. Also, an important

NO, it dose not work, the software does not support keyboards or mouse. But Logitech makes it behave like a trackpad and keyboard on your computer. https://itunes.apple.com/us/app/touch-mouse/id338237450?mt=8